The disclosure of Peters U.S. Pat. No. 6,283,230 entitled METHOD AND APPARATUS FOR LATERAL WELL DRILLING UTILIZING A ROTATING NOZZLE, issued Sep. 4, 2001, as well as the disclosures of my co-pending U.S. patent application Ser. No. 12/350,707 and U.S. Provisional Patent Application Ser. Nos. 61/044,552 and 61/044,639, filed Apr. 14, 2008, are hereby incorporated herein by reference in their entireties.
A large number of wells have been drilled into earth strata for the extraction of oil, gas, and other material therefrom. In many cases, such wells are found to be initially unproductive, or decrease in productivity over time, even though it is believed that the surrounding strata still contains extractable oil, gas or other material. Such wells are typically vertically extending holes including a casing usually of mild steel pipe having an inner diameter of from just a few inches to about eight (8) inches or more in diameter for the transportation of the oil, gas or other material upwardly to the earth's surface.
In an attempt to obtain production from unproductive wells and increase production in under producing wells, as well as for improving production from wells generally, methods and apparatus for cutting a hole in the well casing and forming a lateral passage therefrom into the surrounding earth strata are known. Reference for instance, my previous Peters U.S. Pat. No. 6,283,230, which utilizes tubing having a free end including a nozzle through which fluid is discharged for drilling a lateral passage, which tubing and nozzle are advanced laterally from down hole apparatus, e.g., a kick-off shoe unit, into the lateral passage as the passage is increased in length. The kick-off shoe unit has an internal passage or elbow connecting with a laterally facing opening through which the tubing extends, and from which the tubing is advanced into and through a hole in the well casing and into the lateral passage in the formation. The tubing is also withdrawn from the lateral passage through the lateral opening and elbow of the kick-off shoe.
During the lateral drilling operation, whether using a rotating nozzle or stream as disclosed in my above-referenced patent, or other apparatus, cuttings and other particles will be generated and must be evacuated from the passage. If these remain in the passage, they can accumulate and build up, so as to impede or prevent movement of the cutting apparatus, which can include advancement, withdrawal, and/or rotational movements. Accumulated cuttings and other particles can also impede further movement and evacuation of the particles, and can even prevent removal of the drilling apparatus from the passage, so that forced extraction must be attempted or the lateral passage and down hole drilling apparatus abandoned, resulting in downtime and added cost. To avoid these problems, at least some of the fluid discharged from the nozzle or nozzles will be directed rearwardly through the drilled lateral passage so as to exit through the connecting hole in the casing, for carrying at least a substantial portion of the cuttings and other particles from the passage. The pressure and force of the exiting fluid can vary, for a variety of reasons, including the level of the hydrostatic pressure in the well, the composition of the formation and ability to absorb fluid, and the pressure and volume of the fluid discharged from the nozzle. In any event, the fluid pressure should always be sufficient for drilling satisfactorily, and for carrying the particles and other cuttings from the lateral passage to avoid the above problems.
On the one hand, it is desirable for the fluid and cuttings to be ejected forcefully from the lateral passage and into the well, so as not to accumulate and lodge in the lateral passage, and this is facilitated by decreasing the hydrostatic pressure in the well, as disclosed in my earlier patent. But, on the other hand, when the fluid is discharged forcefully from the lateral passage, the cuttings can in turn be forced into the opposing laterally facing opening of the down hole apparatus, including into the elbow of the kick-off shoe. This creates a resulting problem of the cuttings and other particles interfering with the movement of the drill apparatus, e.g., my flexible tubing, in the shoe, namely, impeding the rotation and/or advancement and/or withdrawal of the tubing through the shoe, so as to correspondingly do the same in the lateral passage. Cutting and other particles can also enter the elbow of the kick-off shoe when drilling through the casing, and cause problems with operation and movement of that drilling apparatus also, whether a liquid jet or mechanical cutter is used.
A laterally opening of the kick-off shoe will be beside and in opposing relation to the inner surface of the well casing and the hole therein, or the hole in the strata if the lateral passage is formed in an uncased region of the well, such that an interface exists or is defined between the opening and the hole. This interface will typically comprise a relatively small space or gap, on the order of less than 1 to 2 inches, but could also be an abutting relationship. Alternatively, if the lateral passage is formed in a larger uncased region of the well, for instance, in an under-reamed region of the well, below the casing, the interface may be substantial in size, e.g., greater than 2 inches. The drilling apparatus, e.g., the flexible tube or hose and nozzle, will extend and move through this interface. The cuttings are also desirably discharged or ejected from the lateral passage into this interface and so as to be carried away from the laterally facing opening of the shoe, but, in practice, because of the pressure of the carrying fluid, this will often not occur, particularly if the interface is smaller, resulting in cuttings and other particle build-up in the elbow of the shoe and resultant problems as discussed above.
Accordingly, what is sought is a solution to build up of cuttings and other particles in the kick-off shoe unit or other down-hole lateral drilling apparatus, for overcoming one or more of the resultant problems and shortcomings set forth above.